This invention relates to a cutting apparatus for a multiple needle cut pile tufting machine, and more particularly to a knife holder apparatus for a cut pile tufting machine.
Conventionally, the knives utilized in multiple-needle cut pile tufting machines for cooperation with looper hooks form cut pile tufts have been supported in individual knife blocks which are open on the sides and include tracks or guideways for engaging the opposite edges of each knife. Each knife block is provided with a rearward projecting cylindrical stud or rod which is adapted to be rotatably adjustably received in a corresponding hole in a knife bar. This structure permits the knives to be set at the desired tension angles relative to the looper hooks. The holes in the knife bars are disposed at angles to the transverse dimension of the knife bar, which are equal to the pitch angle of the knife blades relative to the looper hooks. Each knife is secured in its knife block by threaded set screws, threadedly received within the knife block for movement toward and away from direct engagement with the edge of each knife.
Other prior art knife holders include knife blocks capable of supporting a multiple numbers of knives, such as two, three, four or eight knives each. Furthermore, in some knife blocks, one set screw may be utilized to secure two knife blades, instead of one.
Examples of typical knife holders for multiple needle cut pile tufting machines are shown in the following U.S. Pat. Nos.: 3,277,852, Card, Oct. 11, 1966; 4,003,321, Card, Jan. 18, 1977; and 4,067,270, Short, Jan. 10, 1978.
Because of the continuous vibration of a multiple needle tufting machine during its operation, considerable stress is exerted upon the rearward projecting cylindrical studs or rods in the typical knife blocks causing the knife blocks to rotate, in turn causing the knives to lose their proper tension angles with their cooperating looper hooks.
Several attempts have been made to provide knife holder apparatus which will rigidly mount the knife blocks relative to the knife bar without depending entirely upon the rearward projecting studs from the knife blocks received within corresponding holes in the knife bar.
In the U.S. Pat. No. 3,757,709to Cobble, issued Sept. 11, 1973, although the rearward projecting stud and its cooperating hole are retained, nevertheless, angular channels or guideways are formed in the front face of the knife bar for receiving the back faces of the corresponding knife bars.
T-shaped slots, similar to the vertically disposed angular channels of the above Cobble U.S. Pat. No. 3,757,709 are incorporated in the face of the knife bar of the Card et al U.S. Pat. No. 4,608,934, issued Sept. 2, 1986, in order to accommodate an elongated bracket fixed to the knife holder and provided with laterally projecting lugs for slidable reception within the corresponding slots of the knife bar. In the Card et al U.S. Pat. No. 4,608,934, the rearward projecting stud is eliminated. However, the vertical slidable bracket is retained in position within its corresponding T-slot by detent set screws 41, 141, and 241. In the Card et al U.S. Pat. No. 4,608,934, the bracket is slidably moved upwardly through its corresponding slot. The upward movement of the bracket and knife holder is arrested when the blades are in their operative position cooperating with the looper hooks, any an arresting pin 38 or arresting set screw 141 or 241. The set screws 41 rely upon their capability of engaging the pack surface 33 of the T-slot when tightened, in order to lock the corresponding bracket and its knife holder in its operative position relative to the knife bar.